None of the answers explain why this works, nor even mentioned the useful-to-know name of this syntax.
The actual reason is because that syntax combines two different syntaxes together. These are:
1- multiple function outputs are always indicated by square brackets, the outputs are written in the form of a comma-separated list, e.g.:
[a,b,c,d] = somefun();
This is explained in the introductory tutorials:
2- one cell array can be converted to (or from) a comma-separated list using this syntax:
somecell{:}
which is equivalent to this comma-separated list:
somecell{1},somecell{2},somecell{3},...
Read more about how comma-separated lists work:
Combine these two different syntaxes into one, to allocate multiple function outputs into one cell array:
[somecell{:}] = somefun();
Add indexing as required.
PS: the syntax somecell{:}=somefun() is meaningless.
